$$a \div ( b - c ) = \frac { a } { b } - \frac { a } { c }$$
$a=0$
$b\neq c\text{ and }b\neq 0\text{ and }c\neq 0$
$b\in \mathrm{R}\setminus c,0$
$a=0\text{ and }c\neq 0$